/* 对于指定的文件描述符打印文件标志 2013-11-05_21:03 */
#include "apue.h"
#include <fcntl.h>

int main(int argc, char *argv[])
{
    int val;
    if (argc != 2)
        err_quit("usage: a.out <descriptor#>");

    if ((val = fcntl(atoi(argv[1]), F_GETFL, 0)) < 0)
        err_sys("fcntl error for fd %d", atoi(argv[1]));

    switch (val & O_ACCMODE) {
        case O_RDONLY:
            printf("read only");
            break;
        case O_WRONLY:
            printf("write only");
            break;
        case O_RDWR:
            printf("read write");
            break;
        default:
            err_dump("unknown access mode");
    }
    if (val & O_APPEND)
        printf(", append");
    if (val & O_NONBLOCK)
        printf(", nonblocking");
#if defined(O_SYNC)
    if (val & O_SYNC)
        printf(". synchronous writes");
#endif
#if !defined(_POSIX_C_SOURCE) && defined(O_FSYNC)
    if (val & O_FSYNC)
        printf(", synchronous writes");
#endif
    putchar('\n');
    exit(0);
}
